The present invention is directed generally to apparatus and methods for the extraction of ion beams from a plasma, and, more particularly, to methods and apparatus for extraction of well-formed, high current ion beams from a plasma utilizing a high extraction voltage in a low perveance extraction system.
The generation of initially well-formed ion beams is essential in ion implantation systems where efficient beam transport is required, and in ion microscopes where high brightness is desirable. In a typical ion implantation system with good beam collimation, the beam is usually transported over a long path, typically 3 to 4 meters. The beam path may include a mass analyzer, deflector plates for beam rastering, and drift regions. The beam transport and handling along this path has generally resulted in a significant loss of beam current. This loss of beam current is particularly significant when a high current beam of ions, such as boron, phosphorous, or arsenic, is desired for applications such as ion implantation. Accordingly, extraction of well-formed, high current ion beams having small divergence and less aberration than those heretofore obtained by conventional extraction techniques is desired to minimize beam current losses in subsequent beam manipulation.